math.atan2 is misbehaving on Windows; this patch
should fix the problem in the same way that
the cmath.phase problems were fixed.
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 72ee0db..d1c4822 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -96,6 +96,42 @@
}
/*
+ wrapper for atan2 that deals directly with special cases before
+ delegating to the platform libm for the remaining cases. This
+ is necessary to get consistent behaviour across platforms.
+ Windows, FreeBSD and alpha Tru64 are amongst platforms that don't
+ always follow C99.
+*/
+
+static double
+m_atan2(double y, double x)
+{
+ if (Py_IS_NAN(x) || Py_IS_NAN(y))
+ return Py_NAN;
+ if (Py_IS_INFINITY(y)) {
+ if (Py_IS_INFINITY(x)) {
+ if (copysign(1., x) == 1.)
+ /* atan2(+-inf, +inf) == +-pi/4 */
+ return copysign(0.25*Py_MATH_PI, y);
+ else
+ /* atan2(+-inf, -inf) == +-pi*3/4 */
+ return copysign(0.75*Py_MATH_PI, y);
+ }
+ /* atan2(+-inf, x) == +-pi/2 for finite x */
+ return copysign(0.5*Py_MATH_PI, y);
+ }
+ if (Py_IS_INFINITY(x) || y == 0.) {
+ if (copysign(1., x) == 1.)
+ /* atan2(+-y, +inf) = atan2(+-0, +x) = +-0. */
+ return copysign(0., y);
+ else
+ /* atan2(+-y, -inf) = atan2(+-0., -x) = +-pi. */
+ return copysign(Py_MATH_PI, y);
+ }
+ return atan2(y, x);
+}
+
+/*
math_1 is used to wrap a libm function f that takes a double
arguments and returns a double.
@@ -236,7 +272,7 @@
"asinh(x)\n\nReturn the hyperbolic arc sine (measured in radians) of x.")
FUNC1(atan, atan, 0,
"atan(x)\n\nReturn the arc tangent (measured in radians) of x.")
-FUNC2(atan2, atan2,
+FUNC2(atan2, m_atan2,
"atan2(y, x)\n\nReturn the arc tangent (measured in radians) of y/x.\n"
"Unlike atan(y/x), the signs of both x and y are considered.")
FUNC1(atanh, atanh, 0,